Method and system for generating a display

ABSTRACT

According to one embodiment of the present invention, a method of displaying an image includes alternating an active state of each of a plurality of light sources. The light sources each generate a light beam when active. The alternating includes deactivating an active light source before an output of a light beam from the active light sources falls below a first predetermined threshold. The alternating further includes activating an inactive light source only after an output of the inactive light source reaches a second predetermined threshold. The method further includes receiving each of the light beams at a modulator. The modulator includes an array of micro-mirror devices.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of image displays and morespecifically to a method and system for providing a more constant lightsource for a display.

BACKGROUND OF THE INVENTION

Generating an image on a projection lens traditionally consists ofutilizing white light generated by a lamp and passed through a colorwheel to produce sequential colored beams of light corresponding tocolor filters in the color wheel, such as red, green, and blue. Thesesequential colored beams of light are combined by a DMD to produce adesired color and provided to the projection lens for later display.This standard process, however, has disadvantages. For example, it mayreduce the quality of the image by creating a rainbow effect on theprojection lens.

Other conventional processes for generating an image on a projectionlens consist of using various light sources instead of a color wheel.These standard processes may reduce the rainbow effect. However, thequality of the image generated may also be reduced by the heat generatedby the light sources. In particular, keeping a light source activatedfor too long causes the brightness of each light source to decrease.This, in turn, decreases the quality of the image generated.

SUMMARY OF THE INVENTION

In accordance with the present invention, disadvantages and problemsassociated with previous techniques for installing blast doors may bereduced or eliminated.

According to one embodiment of the present invention, a method ofdisplaying an image includes alternating an active state of each of aplurality of light sources. The light sources each generate a light beamwhen active. The alternating includes deactivating an active lightsource before an output of a light beam from the active light sourcesfalls below a first predetermined threshold. The alternating furtherincludes activating an inactive light source only after an output of theinactive light source reaches a second predetermined threshold. Themethod further includes receiving each of the light beams at amodulator. The modulator includes an array of micro-mirror devices.

According to one embodiment of the present invention, a method ofdisplaying an image includes alternating an active state of each of aplurality of lights sources. The output of the light beam generated byeach light source is controlled by the amount of input provided to thelight source. The method also includes causing the active light sourceto generate a light beam at a constant output while the light source isactive by changing over a time interval the input to an active lightsource. The method further includes receiving each light beam at amodulator. The modulator includes an array of micro-mirror devices.

Certain embodiments of the invention may provide one or more technicaladvantages. A technical advantage of one embodiment may be thatdeactivating an active light source before the brightness of that lightsource falls below an unacceptable brightness threshold keeps thebrightness of the light source within a range where the quality of theimage is not diminished. Similarly, restricting the light source frombeing activated before the light source is capable of generating anacceptable starting brightness further allows the brightness to remainwithin a range where the quality of the image is not diminished. As aresult, the quality of the image generated may increase.

A technical advantage of a further embodiment may be that increasing theamount of input received at a light source over time causes thebrightness from the light source to remain constant throughout the timewhen light source is active. As a result of keeping the brightness ofthe light source constant, the quality of the image generated does notsuffer from a reduction in quality.

Certain embodiments of the invention may include none, some, or all ofthe above technical advantages. One or more technical advantages may bereadily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a block diagram of an example conventional image displaysystem;

FIG. 1B is a block diagram of image display system according to theteachings of the invention;

FIG. 2A is a bar graph describing the brightness level of light sourcesover time;

FIG. 2B is a bar graph describing the brightness of light sources overtime when the active state of each light source is alternated at a rateabove 360 Hz;

FIG. 2C is a flowchart describing a method for alternating the activestate of each light source of a plurality of light sources;

FIG. 3A is a compilation of two graphs displaying the brightness overtime generated by light sources in relation to the input to the lightsources over time; and

FIG. 3B is a compilation of two graphs displaying the brightness overtime generated by light sources in relation to the input to the lightsources over time.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Embodiments of the present invention and its advantages are bestunderstood by referring to FIGS. 1A through 3B of the drawings, likenumerals being used for like in corresponding parts of the variousdrawings.

FIG. 1A is a block diagram of an example conventional image displaysystem 10. According to the illustrated embodiment, conventional system10 generally includes a lamp 14, a color wheel 18, a digitalmicro-mirror device (DMD) 22, and a projection lens 26. Conventionalsystem 10 generates an image on projection lens 26 by utilizing whitelight generated by lamp 14 and passed through color wheel 18 to producesequential colored beams of light 20 corresponding to color filters incolor wheel 18, such as red, green, and blue. These sequential coloredbeams of light 20 are combined by DMD 22 to produce a desired color andprovided to projection lens 26 for later display. DMD 22 is discussedfurther in reference to FIG. 1B.

FIG. 1B is a block diagram of image display system 100 according to theteachings of the invention. System 100 does not include a color wheel,but rather utilizes a plurality of different lights sources 114 a-c.System 100 also includes a light source controller 110, a DMD 122, and aprojection lens 126. As described in greater detail below, system 100may allow light source controller 110 to activate and deactivate theplurality of light sources 114 so that a brightness from each lightsource 114 remains above a predetermined threshold.

Light source controller 110 refers to any device operable to activateand deactivate light sources 114. Light source controller 110 controlswhich light sources 114 are active at any given moment. In oneembodiment, light source controller 110 activates only one light source114 at a time. Therefore, while one light source 114 is active, the restof the plurality of light sources 114 are inactive. In a furtherembodiment, light source controller 110 may refer to multiple lightsource controllers 110. For example, system 100 may include a lightsource controller 110 for each light source 114. Light source controller110 is discussed further in reference to FIGS. 2A, 2B, and 2C.

Light sources 114 may refer to any light sources, such as, for example,Light Emitting Diodes (LEDs), lasers, or any other suitable source thatprovides a desired frequency or frequencies of light. In particularembodiments, each light source 114 may comprise a LED. Unlike broad-bandlight which must be filtered using a color wheel, as seen inconventional system 10, to separate the light into its red, green, andblue components, LEDs may be used to generate “field sequential” imagesof red, blue, and green components. In particular embodiments, lightsources 114 may emit beams of narrow-band light of different colors. Inanother embodiment, light sources 114 may comprise lasers.

In the illustrated embodiment, light sources 114 include light source114 a, light source 114 b, and light source 114 c. In one embodiment,light source 114 a may be selected to emit light beam 118 a. Light beam118 a may include light selected within a desired wavelength range. Forexample, light source 114 a may emit light beam 118 a of a wavelength onthe order of 400-475 nanometers. Thus, in this example, light source 114a may emit blue light. Light source 114 b may be selected to generatelight beam 118 b in a wavelength range that is different from (or incertain circumstances, the same as) that of light wave 118 a. Forexample, light beam 118 b may include light selected within a desiredwavelength range on the order of 485-570 nanometers. Thus, in thisexample, light source 114 b may emit green light. Light source 114 c maybe selected to emit light beam 118 c in a wavelength range that isdifferent from (or in certain circumstances, the same as) that of lightbeam 118 a and light beam 118 b. For example, light beam 118 c mayinclude light selected within a desired wavelength range on the order of610-690 nanometers. Thus, in this example, light source 114 c may emitred light.

The number of light sources 114 and the selection of colors are merelyexamples. Any number of light sources 114 may be selected to emitappropriate beams of light of any desired wavelength range suitable forupgraded system 100. Thus, light sources 114 may be selectively designedto emit beams of primary colors, beams of secondary colors, or beams ofwhite light. Light sources 114 may be chosen to selectively emit anyappropriate color or range of colors. Accordingly, light sources 114 mayinclude any suitable number of LEDs (or other suitable type) selected togenerate any combination of colors. Additionally, each light source 114may comprise multiple LEDs emitting either the same or different colors.

Digital micro-mirror device (DMD) 122 refers, in the illustratedexample, to a micro electromechanical device comprising an array ofhundreds of thousands of individually tilting micro-mirrors. In a flatstate, each micro-mirror may be substantially parallel to projectionlens 126. From the flat state, the micro-mirrors may be tilted, forexample, to a positive or negative angle to alternate the micro-mirrorsbetween an “on” and an “off” state. To permit the micro-mirrors to tilt,each micro-mirror attaches to one or more hinges mounted on supportposts, and spaced by means of an air gap over underlying controlcircuitry. The control circuitry provides electrostatic forces, based atleast in part on image data received at DMD 122. The electrostaticforces cause each micro-mirror to selectively tilt. Light beams 118received on the micro-mirror array may be reflected by the “on”micro-mirrors to projection lens 126. Additionally, light beams 118 maybe reflected by the “off” micro-mirrors towards a plurality of lightdumps, not shown. The pattern of “on” versus “off” mirrors (e.g., lightand dark mirrors) forms an image that is projected by projection lens126. In various embodiments, DMD 122 is capable of generating variouslevels or shades for each color received.

In the illustrated embodiment, light source controller 110 is capable ofcontrolling the brightness of light beams 118 a-118 c from light sources114 a-114 c, respectively, so that the brightness of light beams 118a-118 c remains above a threshold of unacceptable brightness.Traditionally, a thermal image display system includes one single lightsource shining light through a color wheel, as seen in FIG. 1A. However,the rotation of the color wheel from one color to the next may cause arainbow effect on the projection screen that is visible to the humaneye. Therefore, the image generated by the conventional image displaysystem may be subject to improvement by eliminating the color wheel.

Certain embodiments of the present invention are capable of providinglight in a manner that does not require a color wheel. For example, thesingle light source shining through a rotating color wheel is replacedwith a plurality of light sources generating light beams of colors,which in some instances may be substantially similar to those producedby the color wheel. By using various light sources, any rainbow effectcaused by the color wheel is no longer present in the image generated bythe image display system due to the higher cycle rates now practicablein systems without a color wheel.

However, even without the color wheel, the quality of the image maystill be reduced by the heat of the image display system. In particular,heat generated by the light source causes the brightness of each lightsource to decrease because the operating characteristics of certainlight sources are affected by the temperature at which the light sourceoperates. This, in turn, decreases the quality of the image generated bythe image display system because the brightness of the light generatedby the light source will vary based on the lights source's temperature,rather than being constant. Thus, the longer each light source isactively generating light beams, the lower the brightness from eachlight source becomes, in one embodiment, and the lower the quality ofthe image becomes as a result. This problem may be reduced by limitingthe time that each light source is continuously on. This may be achievedby controlling the rate at which each light source is activated anddeactivated.

According to example embodiments of the invention, each light source isboth activated for only the amount of time when the brightness isacceptable, and then kept inactive, allowing the light source to cool,until the light source is capable of generating an acceptable startingbrightness. Deactivating an active light source before the brightness ofthat light source falls below an unacceptable brightness threshold keepsthe brightness of the light source within a range where the quality ofthe image is not diminished. Similarly, restricting the light sourcefrom being activated before the light source is capable of generating anacceptable starting brightness further allows the brightness to remainwithin a range where the quality of the image is not diminished. As aresult, certain embodiments of the present invention may increase thequality of the image generated by an image display system.

FIG. 2A is a bar graph describing the brightness level of light sources114 a-c over time. The vertical axis represents the brightness of thelights sources 114 a-c and the horizontal axis represents time. Astarting brightness level 130 and a threshold brightness level 134 areillustrated by the horizontal dashed lines. Transition points 138 areillustrated by the vertical lines. Transition points 138 refer to thetime at which one light source 114 turns on and another light source 114turns off. For example, the time between transition point 138 a andtransition point 138 b may refer to the time at which a first lightsource 114 emits, in one embodiment, red light. Therefore, transitionpoint 138 b refers to the point in time at which the light sourceemitting red light turns off and the point in time at which a secondlight source, emitting blue light in one embodiment, turns on. As aresult, blue light is emitted between transition point 138 b andtransition point 138 c. Transition point 138 c may refer to the point intime when the second light source 114, emitting blue light in oneembodiment, is turned off and a third light source 114 is turned on toemit, in one embodiment, green light. Therefore, the combination oftransition points 138 a-d refers to one complete cycle of light sources114 a-c. Transition points 138 d-g may refer to further transition timeswhen the above cycle is repeated. In a further embodiment, the point intime at which one light source 114 is turned off and the point in timeat which another light source 114 is turned on may not be identical. Forexample, two lights sources 114 may be turned on and remain active atthe same time.

Starting brightness level 130 refers to the brightness level requiredbefore light source 114 is activated by light source controller 110.According to the illustrated embodiment, starting brightness level 130is the same for each light source 114, but they could vary, if desired.Threshold brightness level 134 refers to the brightness level of lightsources 114 at which it is desired to turn off the corresponding lightssources 114 to avoid the image generated by upgraded system 110 frombeginning to diminish in quality. This may correspond to the level atwhich quality begins to diminish or may correspond to any suitablethreshold level desired. Keeping the brightness for each light source114 above threshold brightness level 134 causes the generated image tonot diminish in quality.

In the illustrated embodiment, the brightness of each light source 114is allowed to reach threshold brightness level 134 before the lightsource 114 is deactivated. Because the light source 114 remains activelong enough to reach threshold brightness level 134, the image generatedby upgraded system 110 may diminish in quality, depending on theselection of the threshold brightness level 134. Therefore, even thoughonly one light source 114 is active at one given time, in thisembodiment, and each light source 114 is kept inactive until it is coolenough to generate brightness at starting brightness level 130, thequality of the image still diminishes. In one embodiment, eachrespective brightness of light sources 114 a-c diminishes to thresholdbrightness level 134 or below when one cycle of alternating theactivation/deactivation of all light sources 114 a-c is completed at 360Hz or lower. Therefore, in the illustrated embodiment, each cycle (forexample, transition point 138 a through transition point 138 d) occursat a frequency of 360 Hz or lower. As a result, the successiveactivation of one light source (such as light source 114 a) occurs at afrequency of 360 Hz or lower.

FIG. 2B is a bar graph describing the brightness of light sources 114a-c over time when the successive activation of each light source 114a-c occurs at a frequency greater than 360 Hz. FIG. 2B includes abrightness level 230, threshold brightness level 234, and transitionpoints 238. Transition points 238 are substantially similar totransition points 138 of FIG. 2A. Likewise, threshold brightness level234 is substantially similar to threshold brightness level 134 of FIG.2A and starting brightness level 230 is substantially similar tostarting brightness level 130 of FIG. 2A. In FIG. 2B, each light source114 is activated when capable of generating starting brightness level230 and deactivated before its brightness reaches threshold brightnesslevel 234, causing the brightness to remain within a range where theimage quality does not diminish. Therefore, the image generated does notsuffer from a reduction in quality. In the illustrated embodiment, lightsource controller 110 both restricts each light source 114 from becomingactive until the light source 114 is capable of producing startingbrightness level 230, and also deactivates each light source 114 priorto its brightness reaching threshold brightness level 234. In theillustrated embodiment, one cycle of activation/deactivation of alllight sources 114 a-c is completed at 1440 Hz. Therefore, each cycle(for example, transition point 238 a through 238 d) occurs at afrequency of 1440 Hz. As a result, the successive activation of onelights source (such as light source 114 a) occurs at a frequency of 1440Hz.

FIG. 2C is a flowchart describing a method for alternating the activestate of each light source of a plurality of light sources. The exampleacts may be performed by light source controller 110, as discussed abovewith reference to FIG. 1B, or by any other suitable device, such asmultiple light source controllers 110. The method starts at step 300. Atstep 302, a light source is activated. In one embodiment, the activelight source emits a light beam at a brightness substantially equal tothe starting brightness level of each light source of the plurality oflight sources. The heat generated by the active light source causes thebrightness of the light source to diminish over time. At step 304, thelight source is deactivated prior to the brightness of the light sourcereaching a threshold brightness level. In one embodiment, this allowsthe image generated by the image display system to not diminish inquality.

Once deactivated, the light source begins to cool down, allowing itspotential brightness level to increase. In one embodiment, the lightsource is not activated again until it is cool enough to generate abrightness substantially equal to the starting brightness level. At step306, the method returns to step 302 to activate the next light source ofthe plurality of light sources. In one embodiment, this causes thesuccessive activation of each light source to occur at a frequencygreater than 360 Hz. In one embodiment, the successive activation ofeach light source occurs at a frequency between 361 Hz and 1,440 Hz. Ina further embodiment, the successive activation of each light sourceoccurs at a frequency between 1,440 Hz and 2,880 Hz. The successiveactivation of each light source occurs, in a further embodiment, at afrequency, between 2,880 Hz and 5,760 Hz. In a further embodiment, thesuccessive activation of each light source occurs at a frequency between5,760 Hz and 12,000 Hz. Although the illustrated embodiment describesthe alternation of light sources 114 a-c, more or fewer light sourcesare contemplated. At step 308, the method ends as a result of the imagedisplay system being turned off.

In one embodiment, alternating the activation and deactivation of eachlight source causes only one light source of the plurality of lightsources to be active at one time. In another embodiment, the activationof two or more light sources may overlap. In a further embodiment,alternating the lights sources at a rate which keeps the brightnessabove the threshold brightness level causes the lights sources to beactive for a shorter period. As a result, less heat is generated.Therefore, the increased rate of alteration, in one embodiment, reducesthe amount of heat transfer required in the image display system.

FIG. 3A is a compilation of two graphs displaying the brightness overtime generated by light sources 114 in relation to the input to lightsources 114 over time. According to the illustrated embodiment, lightsources 114 are activated with a starting brightness level 330. Startingbrightness level 330 is substantially similar to starting brightnesslevel 230 of FIG. 2B and starting brightness level 130 of FIG. 1B. Asdiscussed in FIG. 2A and 2B, the brightness of each light source 114diminishes over time as a result of the build up of heat in imagedisplay system. In one embodiment, the quality of an image generated byimage display system is reduced by the diminishing brightness of eachlight source 114.

According to the illustrated embodiment, the brightness of light source114 is determined by the amount of input 332 received at the lightsource 114. In the illustrated embodiment, input 332 is only shown forone light source 114. Therefore, input 332 between transition points 338a and 338 b determines the brightness over time of one light source 114,shown by bar 334 a. Input 332 between transition points 338 d and 338 edetermines the brightness over time of the same light source 114 lateron in time, shown by bar 334 b. Input 332 comprises any suitable energyused by light sources 114 to generate light beams 118. For example,input 332 may refer to voltage or current. In the illustratedembodiment, when light source 114 is inactive, light source 114 does notreceive any input 332. Alternatively, when light source 114 is active,light source 114 receives a constant amount of input 332. Asillustrated, despite receiving a constant input 332, the brightness oflight source 114 diminishes over time as a result of the build-up ofheat. Thus, by keeping the input constant, the brightness of lightsource 114 does not remain constant. Instead, the brightness maydiminish.

FIG. 3B, describing an alternative embodiment of the present invention,shows a compilation of two graphs displaying the brightness over timegenerated by light sources 114 in relation to the input to light sources114 over time. FIG. 3B illustrates a starting brightness level 430 andinput 432. Starting brightness level 430 is substantially similar tostarting brightness level 330 of FIG. 3A. Likewise, input 432 issubstantially similar to input 332 of FIG. 3A. Additionally, similar toFIG. 3A, the illustrated embodiment only shows input 432 for one lightsource 114. Therefore, input 432 between transition points 438 a and 438b determines the brightness over time for one light source 114, asrepresented by bar 434 a. Input 432 between transition points 438 d and438 e determines the brightness of the same light source 114 later on ittime, as represented by bar 434 b.

In the illustrated embodiment, the brightness of light sources 114 isbelow starting brightness level 430; however, the brightness of thelight sources 114 remains constant throughout the active state of thelight source 114. This constant brightness is the result of anon-constant input 432. By increasing the amount of input 432 receivedat light source 114 over time, the brightness from light source 114 alsoincreases over time. This increase in brightness counters the decreasein brightness, discussed above in FIG. 3A, caused by the build-up ofheat. In the illustrated embodiment, the diminishing brightness causedby the build-up of heat and the increasing brightness caused by theincrease of input 432 cancel each other out, causing the brightness oflight source 114 to remain constant throughout the time when lightsource 114 is active. As a result of keeping the brightness of lightsource 114 constant, the quality of the image generated by image displaysystem does not suffer from a reduction in quality.

Although the illustrated embodiment describes input 432 increasing at aconstant rate, further embodiments of the present invention contemplatea variable rate. Additionally, although initially receiving a lowerinput 432 causes the brightness of light sources 114 to be belowstarting brightness level 430, the constant brightness from lightsources 114, in one embodiment, nullifies any problems associated withstarting the brightness below starting brightness level 430.

Although this disclosure has been described in terms of certainembodiments and generally associated methods, alterations andpermutations of the embodiments and methods will be apparent to thoseskilled in the art. Accordingly, the above description of exampleembodiments does not constrain this disclosure. Other changes,substitutions, and alterations are also possible without departing fromthe spirit and scope of this disclosure, as defined by the followingclaims.

1. An image display system comprising: a modulator comprising an arrayof micro-mirror devices, the modulator operable to receive a pluralityof light beams; a plurality of light sources operable to each generate alight beam; and a control module operable to alternate the transmissionof light beams between the plurality of light sources by: deactivatingan active light source before an output of a light beam from the activelight source falls below a first predetermined threshold; and activatingan inactive light source only after the inactive light source isoperable to transmit a light beam at a second predetermined threshold.2. The system of claim 1, wherein the plurality of lights sourcescomprise light emitting diodes.
 3. The system of claim 1, wherein theplurality of light sources comprise red, blue, and green light emittingdiodes.
 4. The system of claim 1, wherein only one light source of theplurality of lights sources is in an active state at one time.
 5. Thesystem of claim 1, wherein the control module is further operable toalternate the transmission such that successive activation of arespective light source occurs at a frequency greater than 360 Hz. 6.The system of claim 1, wherein the control module is further operable toalternate the transmission such that successive activation of arespective light source occurs at a frequency in a range selected fromthe group consisting of between: 361 Hz and 1,440 Hz, 1,440 Hz and 2,880Hz, 2,880 Hz and 5,760 Hz, and 5,760 Hz and 12,000 Hz.
 7. A method ofdisplaying an image, comprising: alternating an active state of each ofa plurality of lights sources, the plurality of light sources eachgenerating a light beam when active, the alternating comprising:deactivating an active light source before an output of a light beamfrom the active light sources falls below a first predeterminedthreshold; and activating an inactive light source only after an outputof the inactive light source reaches a second predetermined threshold;and receiving each of the light beams at a modulator, the modulatorcomprising an array of micro-mirror devices.
 8. The method of claim 7,wherein the plurality of light sources comprise light emitting diodes.9. The method of claim 7, wherein the plurality of light sourcescomprise red, blue, and green light emitting diodes.
 10. The method ofclaim 7, wherein alternating an active state of each of a plurality oflight sources further comprises activating only one light source of theplurality of light sources at one time.
 11. The method of claim 7,wherein alternating an active state of each of a plurality of lightsources further comprises alternating an active state of each of aplurality of light sources such that successive active states of arespective light source occur at a frequency greater than 360 Hz. 12.The method of claim 7, wherein alternating an active state of each of aplurality of light sources further comprises alternating an active stateof each of a plurality of light sources such that successive activestates of a respective light source occur at a frequency in a rangeselected from the group consisting of between: 361 Hz and 1,440 Hz,1,440 Hz and 2,880 Hz, 2,880 Hz and 5,760 Hz, and 5,760 Hz and 12,000Hz.
 13. A method of displaying an image, comprising: alternating anactive state of each of a plurality of lights sources, the plurality oflight sources each generating a light beam when active, an output of thelight beam controlled by an amount of input provided to the lightsource; causing the active light source to generate the light beam at aconstant output while the light source is active by changing over a timeinterval the input to the active light source; and receiving each lightbeam at a modulator, the modulator comprising an array of micro-mirrordevices.
 14. The method of claim 13, wherein alternating an active stateof each of a plurality of lights sources comprises activating only onelight source of the plurality of lights sources at one time
 15. Themethod of claim 13, wherein the plurality of lights sources compriselight emitting diodes.
 16. The method of claim 13, wherein the pluralityof light sources comprise red, blue, and green light emitting diodes.17. The method of claim 13, wherein changing over a time interval theinput to an active light source comprises changing the input at aconstant rate.
 18. The method of claim 13, wherein changing over a timeinterval the input to an active light source comprises changing theinput at a variable rate.
 19. The method of claim 13, wherein changingover a time interval the input to an active light source comprisesincreasing the input to an active light source.
 20. The method of claim13, wherein the input comprises voltage.